(Reuters) – Police in Pennsylvania found the body of one of four missing men they had been searching for on a sprawling rural farm north of Philadelphia, and a local prosecutor confirmed on Thursday that investigators were treating the case as a murder.

Cadaver-sniffing dogs found the body of 19-year-old Dean Finocchiaro, as well as the remains of other people not yet identified, in a 12-foot (3.7-meter) deep grave on the 90-acre (36.4 hectare) farm this week in Solebury, Pennsylvania.

“This was a homicide. Make no doubt about it,” Bucks County District Attorney Matthew Weintraub said at an overnight news conference. He did not say how Finocchiaro died.

A day earlier, police arrested Cosmo Dinardo, 20, and charged him with stealing and trying to sell a car owned by one of the four missing men, 21-year-old Thomas Meo, of Plumstead Township. They named Dinardo, whose parents own the farm where the bodies were found, as a person of interest in the case.

Dinardo remains in custody.

The two other missing men are Jimi Patrick, 19, of Newtown Township and Mark Sturgis, 22, of Pennsburg. Patrick was last seen by his family on July 5 and the others have been missing since July 7. Finocchiaro lived in Middletown Township.

More human remains were still in the grave and Weintraub said recovery efforts by the Federal Bureau of Investigation, state police, five local police departments and some 40 police cadets would continue on Thursday.

“We’re going to bring each of these lost boys home to their families, one way or another,” Weintraub said.

Police had found Meo’s Nissan Maxima on Sunday at 4 a.m. on the Dinardos’ property and discovered the car’s title, unsigned by Meo, along with his insulin kit for diabetes.

Weintraub said there was no legal exchange of that vehicle and that Meo never went anywhere without his medication.

Dinardo had been arrested earlier in the week for owning a gun he was not allowed to possess under state law because he had previous been involuntarily committed in a mental health facility, prosecutors said. He was released following that arrest after his father posted a bond.